The invention relates to a drilling apparatus for tunnel drive in soil or rock, the head of which is provided with a working tool, and to a method, wherein the drill head forward advance is controlled by means of a protecting tube.
Previously known is a drilling apparatus provided with one working tool a.o. from the U.S. Pat. No. 4,122,683. In the publication a working tool is described which cuts tunnel front wall through rotation. The excavated material runs into the drill head protecting tube and continues to the rear end of the apparatus. The apparatus has a plurality of grippers taking support from the tunnel walls, by means of which the direction of drilling can be adjusted through supporting the protecting tube against tunnel walls and turning either the tool or the movable drill head, for instance, by means of steering cylinders in a desired direction.
The U.S. Pat. No. 2,919,121 introduces a tunnel driving drilling apparatus by means of which excavated material is conducted to the inside of rotating tube. Outside this tube there is also the actual protecting tube enveloping the drill head portion. This tube is supported against the tunnel wall by means of wheels and expanding ring segments, and the direction of the apparatus is effected by these wheels and segments.
The disadvantage of the above solutions is the access of drill waste to the tunnel bottom during the drilling process, allowed by the placement of tool bit portions with relation to the protecting tube. A space is left open between drill bits and the protecting tube, and thus excavated waste simply piles up in this space. It is rather complicated to force the material inside the protecting tube or the conveying tube and not quite possible even on driving a tunnel in unbroken rock.
Due to the fact that a certain quantity of waste always remains in the tunnel in these cases, the alignment of drill head is disturbed since steering is effected through support from the tunnel wall. Especially in the lower tunnel parts, harmful drill waste is left, wedging itself between the protecting tube and the tunnel.